Optical systems, such as retroreflecting or display systems, utilize one or more optical layers for managing incident light. Often, the optical layers are required to have a desired optical transmittance, optical haze, optical clarity, or index of refraction. In many applications, an air layer and a diffuser layer are incorporated into the optical system. Typically, the air layer supports total internal reflection and the diffuser layer provides optical diffusion.
Articles having a structure of nanometer sized pores or voids can be useful for applications based on optical, physical, or mechanical properties provided by their nanovoided composition. For example, a nanovoided article includes a polymeric solid network or matrix that at least partially surrounds pores or voids. The pores or voids are often filled with a gas such as air. The dimensions of the pores or voids in a nanovoided article can generally be described as having an average effective diameter which can range from about 1 nanometer to about 1000 nanometers. The International Union of Pure and Applied Chemistry (IUPAC) have provided three size categories of nanoporous materials: micropores with voids less than 2 nm, mesopores with voids between 2 nm and 50 nm, and macropores with voids greater than 50 nm. Each of the different size categories can provide unique properties to a nanovoided article.